Runaway Black Holes: Cosmic Rockets Leaving Galactic Trails

Astronomers say runaway black holes—spun up by mergers—can be ejected at thousands of km/s, leaving straight contrails of stars as they zip through galaxies. Recent JWST observations in 2025 show potential evidence: a ~10-million-solar-mass hole moving ~1,000 km/s with a ~200,000-light-year contrail and another ~2-million-solar-mass hole in NGC3627 at ~300 km/s with a ~25,000-light-year trail. While these events are rare, such runaways could travel between galaxies, and, in theory, even pass through our Solar System, though the odds are extremely small.